“Why even comment before you know what you’re talking about?” Cuban told CNBC on Monday. The billionaire was responding to Trump’s criticism of players who kneel during the national anthem as an act of protest. “Just because you have a Twitter account doesn’t mean you have to use it,” Cuban told CNBC. “Just because you can say something, doesn’t mean you should.”

Trump first spoke about the NFL protests on Friday. “Wouldn’t you love to see one of these NFL owners, when somebody disrespects our flag, to say, ‘Get that son of a bitch off the field right now, out, he’s fired,'” Trump said at a political rally.

“The President is not going to apologize,” Cuban said. “Are you kidding me? The President should read a book.”